Poly melting transition

Melting transition for poly(dimethylsiloxane) graft segment. 

The melting transition in polymers is conveniently observed by dilatometric measurements of the volume as a function of the temperature. Results thus obtained for poly-(N,N -sebacoyl piperazine) are shown in Fig. 129, and for poly-(decamethylene adipate) by the lowest curve in Fig. 130. Most of the melting, as evidenced by the abnormal increase in volume, occurs within a range of 10°, and it terminates abruptly at a temperature which may be defined within 0.5°. The data shown were obtained by raising the temperature... 

The melting transition temperature and the heat of fusion of poly(nHAMCL) prepared from various alkanoic acids are collected in Table 5. The glass transition temperatures of poly(nHAMCL)s are usually between -30°C and -20°C. 

Seki and Tirrell [436] studied the pH-dependent complexation of poly(acrylic acid) derivatives with phospholipid vesicle membranes. These authors found that polyfacrylic acid), poly(methacrylic arid) and poly(ethacrylic acid) modify the properties of a phospholipid vesicle membrane. At or below a critical pH the polymers complex with the membrane, resulting in broadening of the melting transition. The value of the critical pH depends on the chemical structure and tacticity of the polymer and increases with polymer hydro-phobicity from approximately 4.6 for poly(acrylic acid) to approximately 8 for poly(ethacrylic acid). Subsequent photophysical and calorimetric experiments [437] and kinetic studies [398] support the hypothesis that these transitions are caused by pH dependent adsorption of hydrophobic polymeric carboxylic acids... 

Most interesting are the effects of salt complexation on the mesomorphic behavior of liquid crystalline crown ethers and liquid crystalline crown ether polymers. Sodium triflate was added to poly(17) [34] and poly(25) (Scheme 14) [39]. The enantiotropic nematic and smectic phases of poly(17) were changed dramatically [40]. With increasing amounts of salt, the clearing temperatures are shifted to higher values while the melting transition increases only slightly. 

Melting Transition Typical 360 MHz proton NMR spectra of proflavine poly(dA-dT) complexes, Nuc/D = 24 and Nuc/D = 8, in 1 M NaCl solution at temperatures below the midpoint for the dissociation of the complex are presented in Figures 17A and B respectively. The stronger base and sugar resonances can be readily resolved from the weaker proflavine resonances (designated by asterisks) in the presence of excess nucleic acid (Figure 17) so that the resonances of the synthetic DNA and the mutagen can be monitored independently of each other. 

The melting transition of the daunomycin poly(dA-dT) complex can also be monitored at the nucleic acid resonance line widths and the data for the adenosine H-8 resonance are plotted in Figure 28. The resonance is very broad at temperatures below the melting transition of the complexes (dashed curves in Figure 28) indicative of stiffening of the synthetic DNA by the bound anthracycline ring. 

Griffith, J. H., and B. G. RA.nby Dilatometric measurements on poly (4-methyl-l-pentene), glass and melt transition temperatures, crystallization rates and unusual density behavior. J. Polymer. Sci. 44, 369—381 (1960). 

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